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Last Updated on August 9, 2022 by Editor Futurescope
Carbon dioxide removal from the air can be costly, and it often requires large-scale land and energy consumption. A new, portable solution has been proposed by researchers to capture and store carbon dioxide from retrofitted train cars as they shuttle around on their normal routes.
The concept, outlined in a paper published in the journal Joule, The capture of carbon dioxide could be done for less than fifty US dollars per metric ton. According to the World Resources Institute, the cost of DAC (direct air capture) systems today ranges from $250 to $600 depending on the technology used, energy choice, and scale.
As trains chug along, they suck carbon dioxide out of the air. These vehicles have been designed to take advantage of green energy sources, direct air capture–an up-and-coming technology that will need to be scaled up fast to meet climate goals–and a chassis that resembles Thomas the Tank Engine.
How it Works
The process is not complicated (“It’s one of these things that’s elegant in its simplicity. I mean, it’s not that simple,” Ozin said.) The level of carbon dioxide in our atmosphere is currently around 417 parts per million. Special materials called Sorbents can capture greenhouse gases and store them in liquid or solid form, the concentrated product can then be turned into fuel or buried underground.
The most difficult part of the whole process is ensuring that enough air flows past the sorbent for it to be effective. Other direct air capture systems use massive fans to circulate air past a sorbent, But powering the fan becomes an energy challenge in and of itself that can end up releasing carbon dioxide as the system captures the gas.
The chamber is designed to collect one day’s worth of CO2, says Bachman. The speed of a train directly impacts how much CO2 it can capture – the faster the train, the more CO2 it can absorb, and the quicker it reaches capacity. The air collection for a faster train takes around 45 minutes, while it takes slower trains around an hour or 1.5 hours. The desorption cycle for capturing CO2 takes around 5 to 10 minutes. The high-speed train collects air as it moves, eliminating the need for energy-intensive fan systems used in stationary Direct Air Capture operations.
The capture of CO2 from the air is a process that happens in cycles, explains Bachman. The device uses large intakes of air to extend into the slipstream of the moving train, pulling in ambient air and funneling it into the large cylindrical CO2 collection chamber. After the air has been taken in, the chamber is closed with hatches, and the process of taking the CO2 out of the air begins. The air goes through a chemical process that separates the CO2, and the carbon dioxide-free air then travels out of the back or underside of the car, re-entering the atmosphere. The process of separating the CO2 from the air is known as adsorption. When a set amount of CO2 has been captured, the chamber is closed and the gas is collected, concentrated, and stored.
The air collection chamber is the largest part of the CO2 rail car, taking up 85 percent of its space. The massive CO2 reservoir located at the rear of the ship is 15 tonnes. When there is a crew change or fueling stop, that small reservoir is emptied in a regular CO2 tank car.
In 2021, Bachman founded CO2Rail, A company based in Texas is working on developing direct air capture systems for trains. The motion of the trains would provide an alternative to the static, fan-based systems.
CO2Rail is more than a pipe dream, it’s a plan to capture carbon emissions and put them to good use. Bachman said that the company aims to test out their first full-scale units in a year. Within a decade, he hopes to see direct air capture units on the backs of cargo or passenger trains, sucking up carbon emissions and helping to save the planet.
CO2Rail Company will convert existing rail tank cars into CO2-carrying cars, and aims to have the first cars on the rails in 2023. In the United States, a railroad must be recertified by the Federal Rail Administration every so often. Bachman: ”Once that is completed and the kinks are worked out, by 2024 we can start producing on a bigger scale, starting with 5 or 10 wagons”.
The researchers estimate that an average freight train could help reduce carbon dioxide emissions by up to 6,000 metric tons every year. CO2Rail is now negotiating with a potential funding partner, and if things go well, it plans to start construction on its DAC train car in early 2023.
In order to mitigate the worst effects of climate change, most scientists agree that we need to keep global temperatures at or below 1.5 degrees Celsius above pre-industrial levels. Halting all current CO2 emissions is not enough to accomplish this goal, we need to be more dramatic — The Intergovernmental Panel on Climate Change has estimated that we need to remove 10 billion metric tons of this molecule from the atmosphere every year.